The present invention relates to a deceleration apparatus for a motor and a drive circuit for use in a motor deceleration apparatus or a control apparatus for use in a sewing machine, and more particularly to a deceleration apparatus for a motor and a drive circuit for use in a motor deceleration apparatus or a control apparatus for use in a sewing machine applicable to a general purpose use motor for operating a regenerative brake and applicable suitably to a deceleration apparatus of an alternating current (AC) servo motor for use in an industrial sewing machine.
In a conventional motor, for example in a motor for use in a sewing machine, an electromagnetic clutch braking type motor is employed. In this kind of electromagnetic clutch braking type motor, a time required for braking operation depends upon a mechanical friction braking operation and this braking time is a comparatively short one, and accordingly the motor can stop rapidly.
However, it requires many mechanical elements, and a friction face on a brake ring may wear easily and a life of the motor is apt to be a short one. Further, this kind of electromagnetic clutch braking type motor, has an undesirable manufacturing process and is expensive and further the motor has a large impact noise or mechanical shock noise.
For solving the above stated various defects, it has been known to employ a motor having an electric braking apparatus. Such a motor is disclosed, for example in Japanese Patent Publication No. 35267/1988, in which the motor has the electric braking apparatus. This electric braking apparatus in the motor is a drive control apparatus for use in a sewing machine in which the motor is controlled according to a negative-phase braking.
In the above stated drive control apparatus of the motor for use in the sewing machine, the negative-phase braking is carried out during the entire deceleration process, however there is paid no consideration about an electric load applied to a motor drive element for driving the motor.
When carrying out the electric control of the drive control apparatus for use in the sewing machine, it is necessary to absorb an electric energy or a rotation energy during the rotation of the motor a negative-phase or a regenerative power within a control circuit.
However, for absorbing this electric energy, it is necessary to supply a large electric current with the motor drive element for driving the motor. The motor drive element comprises generally switching elements and diodes.
In the conventional drive control apparatus of the motor for use in the sewing machine, since the large electric current is supplied to the motor drive element during all of the braking operation time or the deceleration operation period, accordingly the motor drive element for driving the motor is apt to be damaged. Further, in the drive control apparatus of the motor for use in the sewing machine having an electric current limiter which is provided for preventing a damage trouble in the motor drive element, it has a problem that it may invite an error during an operation of the electric current limiter.
The above stated undesirable tendencies become remarkable in the drive control apparatus of the motor for use in the apparatus for driving the load having a small friction torque and a large inertia. The industrial sewing machine belongs to an apparatus comprising the above stated load having the small friction and the large inertia.